The present invention relates to an ignition control device as well as to a corresponding ignition control method.
Although it is applicable to any ignition control system, the present invention is discussed with respect to an engine control unit that is located on board a motor vehicle.
Ignition control devices for controlling ignition events for coil ignition systems and devices have essentially two control functions: controlling a desired ignition power over the duration of connection, i.e., the duration of the charging of the ignition coil; and controlling an ignition pulse over the duration of disconnection, i.e., the termination of charging of the coil, using a correct angle.
The ignition power, which in coil ignition systems is metered over a charging time of the coil, is of varying magnitude in accordance with the vehicle system voltage applied to the electrical circuit of the coil and with the time constant of the electrical circuit.
Usually, the specific setpoint values are stored in the control unit as a characteristics field, as a function of the rotational speed and other possible engine parameters.
Conventional ignition control methods are designed for a specific control unit for a specific engine or a specific automobile manufacturer.
If an ignition control device is to be designed for a control unit platform that can be used in any SI engine in accordance with the control and regulation requirements of any customer, then new demands arise for the ignition control method in question.
Conventional ignition output has a substantially self-sufficient operation. An attempt is made to process as much information as possible in the ignition output in parallel and independently, so as to obtain the greatest possible degree of dynamic impact and output precision. For example, a separate rotational speed measurement for the ignition output is customary, being as close as possible, in terms of the angle, to the ignition event, in order to keep the error in the necessary prediction of the rotational angle curve in the dynamic as small as possible. In addition, an attempt is made to calculate the ignition events individually for each cylinder, to the greatest extent possible in parallel fashion.
For example, if it is detected that, due to the advances in the ignition events, the measuring location of the angular velocity must also be shifted, then this shift must be carried out only once and does not have an effect on the calculation of the ignition events for the other cylinders. If an engine control system cannot calculate all of the cylinders individually, for example due to lack of resources, then the attempt is made to form at least one group of cylinders that are similar within the engine.
For an ignition system that is designed for a platform, this method is very expensive, especially in terms of hardware resources. Ignition control systems that require reduced computing expense show that dynamic errors can be sufficiently compensated for by dynamic derivative actions with regard to the ignition angle or the dwell time.
Ignition methods having their own calculation chains avoid application expense, but use more hardware resources, and they also require, depending on the computing architecture, longer job execution times. A further point which characterizes many of the ignition outputs used today is that their output signals are usually fixedly assigned to specific hardware outputs. A method of this type makes project configuration cumbersome when the method is used in a control platform.
Furthermore, a very few ignition output methods check the mixture state of the cylinder that is to be fired. In the new generations of engines, which use plastic intake pipes, the problem of induction pipe explosions has arisen in various ways. This problem can be minimized by first igniting cylinders that are filled in a defined manner.
Therefore, an ignition method has heretofore been lacking that can service as many cylinders as possible using minimal hardware/controller resources, that can easily be configured in accordance with target hardware, and that can be controlled by the injection system.
For outputting angle signals, conventional control units use an angle transmitter wheel, which delivers to the ignition control device pulses that are equidistant in terms of angle. However, for reasons of computational job execution times, the calculation of the ignition events can only take place in most ignition control device architectures in segments, one segment being the angular interval of 720xc2x0 of the crankshaft divided by the number of cylinders, i.e., in a four-cylinder engine, for example, 180xc2x0. Therefore, although the angular positions of the ignition events ascertained in the calculation are measured sufficiently precisely via the angle transmitter wheel and the timer/counter circuits that are customary in the ignition control devices, nevertheless the calculation itself proceeds on the basis of a measured rotational speed, which in a rotational speed dynamic is no longer present at the location of ignition.
Thus, it is desirable to design an ignition control device for the output of ignition events that is able to operate in overall engine control system, which can be used in the greatest possible number of system environments and under the most varied possible system conditions.
Because only a limited framework for control components is available at any one time (e.g., interrupt channels on a predefined controller) for reasons of cost optimization, the device and the method should be able to be realized at a minimal expense, above all with respect to hardware resources. The design of the ignition control method should be modular to the greatest extent possible in order to be able to adjust the ignition control method to various control variants as simply as possible.
The ignition control device according to the present invention has the advantage, with respect to the conventional approaches to the problem, that the design of the ignition control method incorporates the results of analysis of a multiplicity of engine variants. In comparison to the current ignition control methods, the designed ignition output is simpler, more capable of being configured, requires fewer resources, and has clearly defined interfaces, through which the other engine control functions can interact with the ignition output. In particular, the potential interaction with the injection output makes it possible to address the problem of induction pipe backfiring at 0 rotational speed and the problem of uneven starting.
In contrast to the technically current ignition output methods, the described ignition output interacts with other devices for the output of hardware events. In this case, one especially favorable interaction is, for example, querying the status of the injection. In this context, the injection system supplies to the ignition output the information that a defined filling of a cylinder with fuel has taken place. Subsequently, the ignition system will fire this cylinder as a first ignition.
Current ignition outputs begin with the ignition irrespective of the mixture state when the beginning of a 360 degree interval is detected or when simultaneous cylinder detection occurs. In this context, the ignition takes place in undefined mixture states. For example, if a too-lean mixture is ignited, this can result in delayed combustions and in the worst case, even in an explosion of the induction pipe. Furthermore, given a rich mixture, it is possible for the engine to run-up unevenly as a result of pronounced buildup of film on the walls in the induction pipe, which has a disturbing effect on the driving sensitivity, but also potentially on the introduction of exhaust gas reactions.
Conventional technical ignition output methods are not designed with a view to outputting different output patterns simultaneously. Usually, information as to which hardware channels are to be activated in an ignition is fixedly bound to the hardware itself. The ignition output according to the present invention is designed to operate in a plurality of control unit variants with out hardware adjustments and the costs associated therewith. The form and design of the signals delivered from the ignition output to the components can be taken from a table, which is accessed during the program running time of the calculating routines. Therefore, project adjustments of the software are similarly minimized.
In contrast to conventional systems, in the ignition output described, no autonomous evaluation of the transmitter signal is required. The event calculation takes place with regard to the synchronous process that is generally continually present in engine control systems. As a result of the fact that the ignition output also makes use of a general comparator circuit of the rotational speed measuring device, which can be configured on the basis of a comparison of time but also of angle, for angle counting and increment refinement only one single activation line is needed for the calculating unit. If the ignition output is converted to conventional controllers without parallel computing units (so-called economical system), then for the entire ignition output only two interrupt channels are required. If one interrupt is used for sending the current and one interrupt is used for interrupting the current, then any number of cylinders can be served. The assignments of the cylinders and their special modes are realized using correspondingly complex buffer structures. In this manner, controller and hardware resources are saved which can be used by other functionalities. Although the ignition output, built up in this manner, has the characteristic of being dynamically somewhat less current than most conventional methods, nevertheless in trials it has been demonstrated that the output precision achieved is sufficient for the requirements of an SI engine.
According to one refinement, an enabling device is provided for enabling the ignition control value output if an injection has occurred.
According to a further refinement, the ignition control value output device is configured such that it outputs the charging time of the ignition coil device starting from the beginning charging angle by appending on to the charging time in a charging time output mode, and by counting out a charging angle until the occurrence of the ignition event, in an ignition angle output mode.
According to a further refinement, a table device is provided which contains the information that when an ignition event occurs is conveyed to the ignition control value output device.
According to a further refinement, only one single angle/time comparator is used for calculating the beginning charging angle and the ignition angle. This implies that there are only two interrupts, i.e., one for the charging and one for the ignition, irrespective of the number of cylinders in the internal combustion engine.
According to a further refinement, the calculation of the beginning charging angle and the ignition angle generally takes place in a synchronous raster, without a special ignition interrupt.
The latter two refinements create an extremely advantageous timing behavior with regard to the outside.